Electronic transistorized ignition system



Oct. 28, 19,69 M. w. RAYBIN 3,475,648

ELECTRONIC TRANSISTORIZED IGNITION SYSTEM Filer. Jan. 3, 1968 2Sheets-Sheet 1 FOR NEG. GR'ND '6 TO DIST s IQ H.V. I I6 6 m l2 5" 4? 0DIST. POINTS 5 23 FOR POS. GR'ND BATT- IGN. sw.

/ NVEN'T OR.

MEYER W. RAYBIN OctQZB, 1969 x M. w. RAYBIN. 3,475,648

ELECTRONIC TRANSISTORIZED IGNITION SYSTEM Filed Jan. 5, 1968 2 SheetSSheet (PRIOR ART) INVENTOR United States Patent 3,475,648 ELECTRDNICTRANSISTORIZED IGNITION SYSTEM Meyer W. Raybin, 9 Bertlee Drive,Huntington Station, N.Y. 11746 Filed Jan. 3, 1968, Ser. No. 695,473 Int.'Cl. H05b 41/14 US. Cl. 315-206 8 Claims ABSTRACT OF THE DISCLOSURE Thisinvention is an improvement of the transistor assisted ignition systemdescribed in US. Patent 3,252,049 issued May 17, 1966. Addition ofelectrical elements to isolate the spark coil from the DC. batterysupply and to protect the transistor switch from excessive voltage peaksenhances efliciency and improves operating characteristics. Thermalrunaway in the transistor is prevented by use of a pair of seriesconnected diodes in the emitter circuit which insure instantaneouscut-ofl by neutralization of the floating potential and by applicationof a reverse voltage and current to reduce time delay to cut-off.

Background This invention relates to internal combustion engineelectrical distribution systems and has particular reference totransistor assisted ignition systems.

IMy US. Patent 3,252,049 issued May 17, 1966 describes and claims thebasic concept of a. transistor assisted ignition in which a transistorswitching device is interposed between the distributor points and anautotransformer which feeds the high voltage coil (by its magnetic highenergy collapse) of an internal combustion engine. It has been foundthat certain improvements to the basic circuit there described, will actto increase the efficiency of the engine and prolong the life of thecircuit.

Summary of the invention In one such improvement, the battery supply iseffectively disconnected from the high voltage by diode means therebyeliminating DC. current in the primary section of the high voltage coil.In another improvement, the voltage spikes occurring in theauto-transformer are not permitted to reach the transistor, therebypreventing damage to the transistor. In a third circuit change, thecut-off diode in the transistor emitter circuit is kept energized at alltimes to insure instantaneous reaction of the diode to changes in thecircuit operating condition.

Most importantly, however, it has been found necessary to employ a pairof series connected diodes in the emitter circuit rather than one diodealone for thermal protection of the transistor. A power transistor isbuilt to handle heavy currents and by its very nature has appreciableinternal capacitance. This characteristic creates a delay in the risetime to conduction and also a delay in the fall time to cut-off. Thisrise and fall time delay results in high heat dissipation within thetransistor, the heating energy being taken from the power which could beused more advantageously as magnetic energy in the autotransformer. Inorder to remove or minimize the delay time to cut-off, thereby reducingheat dissipation and augmenting the power to the auto-transformer, areverse voltage and current at the transistor base is applied as aninstantaneous step function when the base drive power is removed, i.e.the ignition breaker points are opened. This reverse power is suppliedby the voltage drop across one of the emitter diodes. Also, a powertransistor inherently develops internally what is termed a floatingpotential when it approaches cut-off. The polarity of this floating icepotential is such as to resist cut-off by tending to turn the transistoron. This floating potential is neutralized by the second emitter diode.Thus, one diode supplies the instantaneous reverse power in a stepfunction while the other diode neutralizes the floating potential. Nosingle diode has been developed yet which can supply both voltagesdescribed above (unless two diodes are packaged in one case) thereforethe series connected diodes must be employed. These and other circuitchanges and their advantages will be made clear with reference to theaccompanying drawings, in which:

FIGURE 1 shows the new circuit for an automotive system using a negativeground,

FIGURE 2 is similar to FIGURE 1, but for a positive ground system,

FIGURE 3 is a circuit for the prior art,

FIGURE 4 is an explanatory portion diagram of FIG- URES 1 and 2, andFIGURE 5 is one modification of FIGURE 4.

Description of preferred embodiments For a discussion of the prior artrefer first to FIG- URE 3. FIGURE 3 is essentially that of FIGURE 1 ofPatent 3,252,049 leaving out certain extraneous material and renumberingthe elements. Upon reference to the patent and the complete descriptioncontained therein, it will be apparent that closure of the breakerpoints 20 completes the base-emitter circuit of transistor 2 throughresitor 1, diode 5, closed ignition switch 17, power supply 22 andground 23. Ignition switch 17 is closed by energization of relay winding4 by closing of switch 21. This energization of the base-emitter circuitbrings the transistor 2 into a hard saturated condition, completing theemitter-collector through the primary turns 12a of autotransformer 12,ballast resistor 15, ground 23, power supply 22 and diode 5. Thus, theprimary winding 12a of auto-transformer 12 is energized whenever thedistributor breaker points 20 are closed, and a strong magnetic field isbuilt up in the laminated iron core of auto-transformer 12. When thedistributor breaker points 20 are opened, the transistor 2 goes into acut-off condition, presenting a very high resistance at theemitter-collector terminals, effectively opening the circuit of primarywinding 12a. The collapsing magnetic field in transformer 12 produces astepped up voltage across windings 12a and 12b of the transformer 12which is connected to the primary winding 14a of the high voltage coil14 of the existing ignition system. The secondary coil 14b of coil 14 isconnected sequentially to the engine spark plugs by distribution means(not shown) creating a spark at the appropriate spark plug whichcontinues until the energy stored in the magnetic core of transformer 12is expended. The Zener diode 7 protects the transistor 2 from excessivehigh voltage peaks created in transformer 12.

The circuit just described has certain deficiencies which may detractfrom its universal application. These deficiencies are absent in thecircuit of FIGURES 1 and 2, which circuit forms the basis of the presentinvention. FIGURE 1 shows a negative grounded system while FIGURE 2shows a positive grounded system. With reference now to FIGURE 1, theefliciency of transfer of energy from auto-transformer 12 to primarywinding is enhanced by removing the ballast resistor 15 from the circuitbetween windings 12b and 14a and placing it in series with power supply22. This change will necessitate a change of the values of resistors 1and 3 from those in the circuit of FIGURE 3, to provide the propervoltages to the PNP transistor 2. The more important change, however, isthe addition of a diode 13 in the series circuit between the windings12b and 14a whereby the DC. circuit through windings 12b and 14a andtransistor 2 to power supply 22 will be interrupted, so as to remove anyreverse DC. current from coil winding 14a through winding 12b. Theeffect of this diode 13 is to allow the energy of the magnetic field inthe core of auto-transformer 12 to discharge in a pulse form intowinding 14a thereby increasing the efficiency of energy transfer and toobtain optimum energy at the spark gap of the spark plugs.

When the primary circuit of the auto-transformer in FIGURE 3 is opened,the induced high voltage spike at the junction point of windings 12a and12b will be applied to the collector-emitter circuit and can damage thetransistor 2 and the Zener diode 7. In order to alleviate thiscondition, the peak voltage applied to transistor 2 (when the breakerpoints 20 are opened) is reduced by connecting capacitor 6 across thecollector and emitter leads, connecting RF choke 8 in series with thecollector lead and by connecting another capacitor 10 across the totalwinding 12a and 12b of auto-transformer 12. The capacitor 10 integratesinitially the voltage spike across the total winding 12a and 12b. The RF(radio frequency) choke 8 (air core) provides additional impedance tothe fast voltage spike while capacitor 6 further integrates that portionof the voltage spike which would be reflected to the transistor 2. Thisintegration adds to the total energy at auto-transformer 12 at themoment of power transfer. A resistor of high impedance, resistor 9, isconnected between diodes 5, a and ground 23 and maintains a steadycurrent of from 50 to 100 milliamperes, more or less, to keep the diodes5 and 5a in a conducting state during the transistor cut-off time sothat the base of transistor 2 will see this cut-off voltage conditionfor the full duration of the cut-off time. Diode 5a has been added inseries with diode 5 in the emitter circuit of transistor 2. As explainedearlier, the voltage drop generated across diode 5a creates a stepfunction reverse power which reduces and practically eliminates thedelay time to cutoff in transistor 2 when the breaker points 20 areopened while the voltage drop across diode 5 is a reverse voltage forneutralizing the floating potential generated within transistor 2.FIGURE 2 is similar to FIGURE 1 in all respects except that the polarityof all polarized elements has been reversed. Thus, PNP transistor 2 ofFIGURE 1 has been replaced by an NPN transistor 16, and the polarity ofeach diode 5, 5a 13 and Zener diode 7 has been reversed.

FIGURES 1 and 2 show the improved basic circuit but many modificationstherein are possible within the spirit of the invention. For example,the usual breaker points 20 as shown in FIGURE 4 are operated by a sixlobed cam 30 driven by the shaft 31. It should be realized thatintermittent energization of the base-emitter circuit of transistor 2 or16 can be accomplished in many ways, one of which is that using breakerpoints (open and close cam operated) shown in FIGURE 4. Another example,FIGURE 5 shows a magnetic induction type of breaker circuit. Here a sixlobed cam made of ferrous material 32 is rotated in close proximity toan induction 33 to vary the strength of a magnetic field provided by thestationary magnet 34 which is adjacent or within coil 33. This periodicvariation of the magnetic field induces a pulsed voltage in the coil 33which is amplified in an amplifier 35 if necessary and is then used toenergize the baseemitter circuit of transistor 2 or 16. Alternatively,the breaker points of FIGURES 1, 2 or 3 may be replaced byphoto-electric devices not shown but which act to complete thebase-emitter drive circuit at appropriate times. Therefore, it isapparent that the use of actual switch contacts in the base-emittercircuit is not required and the invention is not so limited but anydevice which will alternately energize and de-energize the base-emittercircuit at the proper times can be used. The term breaker, as used inthe claims, should be interpreted to cover all or any of these possibleconstructions. Also, it should be recognized that the energy storagetransformer 12 need not be an auto-transformer only, but that in certaininstances a two winding transformer may be preferable. Therefore anyreference to the term primary and secondary transformer windings shouldnot be limited to autotransformer windings although such constructiononly is shown in the figures.

My claims are:

1. In a transistor assisted ignition system, having base, emitter andcollector electrodes, breaker means for alternately energizing andde-energizing the base-emitter circuit of said transistor, an energystoring transformer having a primary winding and a secondary winding,said primary winding being connected between the collector in series andthe emitter of said transistor in series with unidirectional powersupply and said secondary winding being connected to ignition devices insaid ignition system, whereby energization of said base-emitter circuitcauses energy to be stored in said transformer, and deenergization ofsaid base-emitter circuit causes said stored energy to be dischargedinto said ignition devices, a pair of diodes connected in series,interposed between said emitter electrode and said power supply in theforward direction to provide a reverse voltage at said base electrodeand to neutralize the floating potential developed internally of saidtransistor whenever said base-emitter circuit is de-energized by saidbreaker means.

2. Apparatus as in claim 1 including first capacitor means connectedacross said primary winding and second capacitor means connected acrosssaid secondary winding.

3. Apparaus as in claim 2 including inductive means connected betweensaid transformer primary winding and said first capacitor means.

4. Apparatus as in claim 1 including resistor means connected betweenthe junction of said emitter electrode and said diodes and said powersupply to maintain sufficient current through said diodes at such timesthat said base-emitter circuit is de-energized by said breaker means toinsure cut-off of said transistor for the full duration of such times.

5. Apparatus as in claim 1 wherein said energy storage transformer is anauto-transformer and including second transformer means interposedbetween said energy storage transformer and said ignition devices, and adiode connected between said transformers in the reverse direction tothereby eliminate a direct electrical path between said unidirectionalpower supply and said second transformer (ignition coil).

6. Apparatus as claimed in claim 1 in which said breaker means includesan induction coil connected between said base and emitter electrodes, amagnet adjacent or within said coil and means for periodically varyingthe magnetic field in said coil due to said magnet to produce a varyingvoltage across said coil.

7. Apparatus as claimed in claim 6 including amplifying means connectedbetween said induction coil and said base electrode.

8. Apparatus as in claim 1 including Zener diode means connected betweensaid collector and emitter electrodes or between collector and baseelectrodes.

References Cited UNITED STATES PATENTS 3,016,477 1/ 1962 Naborowski315--206 3,034,018 5/1962 Rosenberg 3l5--205 3,374,778 3/1968 Dixon123-148 JOHN W. HUCKERT, Primary Examiner R. F. POLISSACK, AssistantExaminer US. Cl. X.R.

